Polymerizable compounds are used for various films. For example, films having uniform alignment can be formed by arranging polymerizable compounds in a liquid crystal state and polymerizing the compounds. The thus-formed films can be used for a polarizing plate, a retardation film, and the like necessary for liquid crystal displays. Also, polymerizable compounds can be used for forming films having a cholesteric structure. In many cases, compositions composed of two or more types of polymerizable compounds are used for satisfying required optical characteristics, polymerization rate, solubility, melting point, glass transition temperature, film transparency, mechanical strength, surface hardness, heat resistance, and light resistance. In this case, the polymerizable compounds used are required to impart good physical properties to the compositions without adversely affecting other characteristics. In particular, the purpose of forming a film having a cholesteric structure requires polymerizable compounds which can be present as a nematic phase or cholesteric phase within a wide temperature range and which have high nematic or cholesteric liquid crystal alignment properties. In addition, when a polymerizable liquid crystal composition is industrially used, high storage stability is required so as to avoid precipitation of polymerizable compounds in components even during long-term storage.
When the film having a cholesteric structure is used as a brightness enhancement film of a display or the like, the film is required to have a small haze value and a uniform cholesteric structure without unevenness. Therefore, polymerizable compounds having high alignment properties in addition to the above-described characteristics are desired. In addition, in order to adjust refractive index anisotropy of a composition to a desired value, not only a polymerizable compound having large refractive index anisotropy but also a polymerizable compound having small refractive ice anisotropy is useful. However, generally known polymerizable compounds having small refractive index anisotropy have low storage stability and thus have the problem of precipitating crystals when a composition containing the polymerizable compounds is allowed to stand at room temperature for a long time. Also, due to low alignment properties, an optically anisotropic body produced by applying the composition on PET and drying the composition has the problem of increasing a haze value and causing unevenness (refer to Patent Literature 1 to Patent Literature 3). On the other hand, an example is reported, in which polymerizable compounds having a tolan skeleton introduced therein are used as liquid crystal materials having a high biaxial index, but any one of the polymerizable compounds has very large refractive index anisotropy, thereby increasing refractive index anisotropy of a composition (Patent Literature 4). Therefore, in order to adjust the refractive index anisotropy of a composition to a desired value, it is necessary to add a polymerizable compound having small refractive index anisotropy, but known polymerizable compounds having small refractive index anisotropy have the problem of unsatisfactory storage stability and alignment properties as described above.